History is full of engineers making (or attempting to make) things out of the wrong stuff, from massive wooden aircraft to boats made of ice and sawdust. [PeterSripol] is attempting to make an ultralight aircraft out of a rather wrong material: cardboard. In the previous installment of the project, a pair of wings was fabricated. In this installment, the wings find their home on an equally mostly cardboard fuselage, complete with rudder and elevator.
The fuselage construction amounts to little more than a cardboard box in the shape of an RC airplane. Doublers provide additional strength in critical areas, and fillets provide a modicum of additional strength around seams. To support the weight of the pilot, a piece of corrugated cardboard is corrugated again, with an additional piece making up the floor. With the addition of a couple of side windows for comfort and visibility, the fuselage is completed, but additional components need to be added.
[Miroslav Hancar] wasn’t satisfied with abusing just a single component for our Component Abuse Challenge. He decided to abuse a whole assembly, in particular, some LED candles.
In this project, LEDs are abused as temperature sensors. When the temperature gets hot enough for long enough, the microcontroller will turn on its LEDs. How? A diode’s forward voltage is temperature-related. By monitoring the forward voltage, the microcontroller can infer the temperature and respond appropriately.
This particular project is really two projects in one, centered around a common theme, heat activation. The first version has four LEDs and, in response to heat, four LEDs flicker to simulate a real candle. The second version is also heat-activated, but it has only one LED. You can snuff out this LED by pinching the top of it with your fingers. You can see a demo of each version in the videos below.
Anything with a laser has undeniable hacker appeal, even if the laser’s task is as pedestrian as sending data over a fiber optic cable. [Shahriar] from [The Signal Path] must agree, and you can watch as he tears down and investigates a fiber optic link made from old HP equipment in the video below.
He starts with an investigation of the block diagram of the transmitter. In the transmitter, the indium gallium arsenide phosphide laser diode emits light with a 1310-nanometer wavelength. Thermal characteristics in the transmitter are important, so there is thermal control circuitry. He notes that this system only works using amplitude modulation; phase modulation would require more expensive parts. Then it’s time to look at the receiver’s block diagram. Some optics direct the light signal to a PIN diode, which receives the signal and interfaces with biasing and amplifying circuitry.
The eccentric shaft and rotor of the Mazda 12A rotary engine. (Credit: Baked Beans Garage, YouTube)
In theory, Wankel-style rotary internal combustion engines have many advantages: they ditch the cumbersome crankcase and piston design, replacing it with a simple, single-chamber design and a thick, plectrum-shaped chunk of metal that spins around inside that chamber to create virtual combustion chambers. This saves weight and maximizes performance-to-weight. Unfortunately, these types of engines are also known for burning a lot of oil and endless seal troubles, especially with early rotary Mazda engines that easily died.
Yet even 1980 versions were not without issues, a case in point is the Mazda 1st gen RX7 with a 12A rotary engine that the [Baked Beans Garage] over at YouTube got their paws on. Starting with unsuccessful attempts to make the car start, the next step was to roll the car into the morgue garage for a full teardown of the clearly deceased engine.
About 35 minutes into the video, we get to the teardown of the engine, with its parts contrasted with those of a newer revision rotary engines alongside illustrations of their functioning, making it as much an autopsy as a detailed introduction to these rotary engines. Technically, they also aren’t the original DKM-style Wankel engines, but a KKM-style engine, as designed by [Hanns-Dieter Paschke]. [Wankel] didn’t like the eccentric KKM design, as he thought it’d put too much stress on the apex seals, but ultimately the more economical KKM design was further developed.
During the autopsy of the 12A revision Mazda engine, it becomes clear that it was likely overheating that killed the engine over the course of years of abuse, along with ‘chatter’ marks of the apex seals destroying the inner chrome coating. This would have compromised compression and with it any chance of the engine running, not unlike a piston engine with badly scored cylinder walls after ingesting some metal chunks.
While the Mazda 12B and subsequent designs addressed many of the issues with the early rotary engines, its use was limited to some sports models, ending in 2012 with the RX-8. The currently produced Mazda MX-30 does use a rotary engine again in its plug-in hybrid version, but it’s only as a range extender engine that drives a generator. Looking at the internals of those Mazda rotary engines, it’s easy to see how complex they are to keep running, but you cannot help but feel a little bit of sadness that these small-but-powerful engines didn’t make much more of a splash.
There is a point where taking technology for granted hides some of the incredible capabilities of seemingly simple devices. Optical mice are a great example of this principle, using what are more or less entirely self-contained cameras just for moving the cursor across your screen. Don’t believe us? Check out this camera made from an old optical mouse from [Dycus]!
For those unfamiliar with optical mice, the sensor used for tracking movement, like a camera, is just an array of photosensitive sensors. This allows a simple on-board microcontroller to convert the small changes from the visual sensor into acceleration/movement information to be sent to the computer.
Proving how capable these sensors can truly be, [Dycus]’s camera manages a whole 30×30 array of picture quality. Along with glorious greyscale, the pictures achieved from such a camera are more than recognizable. Putting together the camera didn’t even require anything crazy beyond the sensor itself. What appears to be a Teensy LC board, basic buttons, and a small screen are essentially everything required to replicate the camera’s functionality. Pictures, both standard and “panoramic”, can be viewed in a variety of color palettes stored on board. Along with a surprisingly impressive feature set, the idea is impressive.
Limitations are often the mother of innovation, no matter if self-imposed or not, as seen here. However, [Dycus] still had a whole 30×30 array to photograph. What about a single pixel? Let’s make it even harder; we can’t look directly at the subject! This is exactly what was done here in this impressive demonstration of clever engineering.
Most of us know that a neon bulb requires a significant voltage to strike, in the region of 100 volts. There are plenty of circuits to make that voltage from a lower supply, should you wish to have that comforting glow of old, but perhaps one of the simplest comes from [meinsamayhun]. The neon is lit from a 9-volt battery, and the only other component is a relay.
What’s going on? It’s a simple mechanical version of a boost converter, with the relay wired as a buzzer. On each “off” cycle, the magnetic field in the coil collapses, and instead of being harvested by a diode as with a boost converter, it lights the neon. Presumably, the neon also saves the relay contacts from too much wear.
We like this project for its simplicity and for managing to do something useful without a semiconductor or vacuum tube in sight. It’s the very spirit of our 2025 Component Abuse Challenge, for which there is barely time to enter yourself if you have something in mind.
Last weekend was Supercon, and it was, in a word super. So many people sharing so much enthusiasm and hackery, and so many good times. It’s a yearly dose of hacker mojo that we as Hackaday staff absolutely cherish, and we heard the same from many of the participants as well. We always come away with new ideas for projects, or new takes on our current top-of-the-heap obsession.
If you didn’t get a chance to see the talks live, head on over to the Hackaday YouTube stream and get yourself caught up really quickly, because that’s only half of the talks. Over the next few weeks, we’ll be writing up the other track of Design Lab talks and getting them out to you ASAP.
If you didn’t get to join us because you are on an entirely different continent, well, that’s a decent excuse. But if that continent is Europe, you can catch us up in the Spring of 2026, because we’re already at work planning our next event on that side of the Atlantic.
Our conferences always bring out the best of our community, and the people who show up are so amazingly positive, knowledgeable, and helpful. It’s too bad that it can only happen a few times per year, but it surely charges up our hacker batteries. So thanks to all the attendees, presenters, volunteers, and sponsors who make it all possible!
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